If you want an answer you must present the information in a concise and complete form. The members of this forum are not your slaves, and they are under no obligation to wade through your confused, convoluted and overly-punctuated postings to extract salient points - that kind of attitude makes you come over as an entitled oik with something to hide.
If I understand correctly you bought your tickets in Spain using a spanish payment card. If that is the case you need to be talking to someone who understands spanish consumer law.
Was your "Full and comprehensive insurance" also from a spanish provider? If so you may need to take expert advice on what is covered by that insurance, because it varies from country to country.
Unless you explicitly identified your wife's special needs at the time of the booking you probably have no rights relating to the change of aircraft or seat locations. You bought standard tickets, and the Ts&Cs for those (available on the booking website) will invariably say the airline can change aeroplane type and seat assignments without notice. In my experience of commercial flying (long, medium and short haul - must be well over a hundred flights over the last 30-40 years) I think the number of times when my initial seat allocations survived through to the flight would be counted on the fingers of one thumb. If you want any great confidence you have to be a high-graded frequent flyer, but even then the only seat allocations that are reliable are the ones made a few days before the flight (in the privileged period when frequent flyers can check in but regular customers can't). If you need special treatment due to disabilities then TELL THE AIRLINE BEFORE YOU BOOK. They may be able to accommodate your needs, but it may need you to buy a more expensive ticket deal.
If your sole reason for not being able to travel is that the US border is closed to you then it's nothing to do with the airline. If that specific risk is not covered by your travel insurance then it's not their problem either. You can try suing the US government if you like - if you happen to like wasting money.
It might be worth asking the insurer under which specific clause(s) they are denying a claim. I have successfully changed the decision of a british travel insurer when I read page 17 of the 16 page policy document and found a list of things that were covered followed by a list of things that were not covered. The final entry in the second list said "anything not included in the first list". This open exclusion (there's a term for it that I can't remember off hand) isn't allowed under English contract law, and when I pointed this out to them the paid up almost by return of post. So ask them which specific clause excludes your claim, and then read the contract.
PDR